JP7601697B2 - chair - Google Patents

Description

The present invention relates to a chair.

Chairs equipped with a lumbar support that can support the lower back of a seated person against the backrest have been known (see, for example, Patent Document 1).

There are various types of conventional lumbar supports that can be adjusted up and down relative to the backrest.

However, most conventional lumbar supports are attached to the backrest using fasteners before the chair is completed.

In other words, conventional chairs do not have lumbar supports that can be attached and detached after the chair is completed, without having to attach and detach fasteners to the backrest.

If the lumbar support can be configured to be detachable from the backrest after the chair is completed, it is desirable to take measures to prevent problems such as the lumbar support unintentionally detaching from the backrest.

JP 2020-058769 A

The present invention was made in light of the above circumstances, and aims to provide a chair with a suitable configuration in which at least a lumbar support that can support the lower back of a seated person can be repositioned vertically relative to the backrest and can be attached and detached without having to attach or detach a fastening device.

That is, the present invention has the following configuration.

The invention described in claim 1 is a chair in which a lumbar support capable of supporting the lower back of a seated person is provided so that its position can be changed in the vertical direction relative to the backrest and it can be attached and detached without attaching or detaching a fastening device, the backrest is provided with left and right side frame members extending in the vertical direction and a tension member stretched between the left and right side frame members, the left and right side frame members are provided with lumbar support holding parts capable of holding the held parts provided at both the left and right ends of the lumbar support, the held parts have one or more protruding parts protruding backward, the lumbar support holding part has a storage groove that extends in the vertical direction and opens forward to accommodate the protruding parts, and a front restricting part that is arranged in front of the storage groove and can restrict the forward movement of the protruding parts, and the front restricting part or the groove forming wall of the side part that can form the storage groove has a notch that allows the protruding parts to pass through when the lumbar support is attached and detached from the backrest.

The invention described in claim 2 is the chair described in claim 1, in which the retained portion has upper and lower protruding portions that are the multiple protruding portions spaced apart in the vertical direction, and the front restricting portion or the groove forming wall is provided with an upper cutout that is the cutout portion that allows the upper protruding portion to pass through, and a lower cutout that is the cutout portion that allows the lower protruding portion to pass through.

The invention described in claim 3 is the chair described in claim 2, in which the shape of the upper protruding portion is set to a shape different from the shape of the lower protruding portion, the shape of the upper cutout is set to a shape corresponding to the upper protruding portion so that the upper protruding portion can pass through, and the shape of the lower cutout is set to a shape corresponding to the lower protruding portion so that the lower protruding portion can pass through.

The invention described in claim 4 is the chair described in claims 1, 2, or 3, in which the front restraint portion is a member separate from the side frame material and is provided on a retaining member attached to the side frame material.

The invention described in claim 5 is a chair described in claims 1, 2, 3, or 4, in which the lumbar support holding portion can hold the protruding portion by sandwiching it in the front-rear direction between the front restricting portion and the inner groove forming wall that can form the storage groove.

The invention described in claim 6 is a chair described in claims 1, 2, 3, 4, or 5, in which the lumbar support comprises a lumbar support body and left and right arm members supported by the lumbar support body, and the retained portion is provided on the outer end of the left and right arm members.

The invention described in claim 7 is the chair described in claim 6, in which the left and right arm members are supported so as to be movable in the left and right direction relative to the lumbar support body.

The invention described in claim 8 is a chair described in claim 7 in which a first engagement portion provided on the lumbar support body engages with a second engagement portion provided on the left and right arm members, so that the left and right arm members can move left and right relative to the lumbar support body, the first engagement portion is configured as a convex portion or an engagement hole that is longer in the width direction than the convex portion, and the second engagement portion is configured as an engagement hole that can engage with the convex portion or a convex portion that can engage with the engagement hole.

The invention described in claim 9 is a chair according to claims 6, 7 or 8, in which the lumbar support body comprises a front body member and a rear body member that is approximately the same size as the front body member and is attached to the back side of the front body member, and the left and right arm members are sandwiched between the front body member and the rear body member.

The invention described in claim 10 is the chair described in claim 9, in which the front body member comprises a front body base made of synthetic resin in the shape of a plate extending in the left-right direction, and a front skin material that covers the front surface and peripheral portion of the front body base, and the rear body member comprises a rear body base made of synthetic resin in the shape of a plate extending in the left-right direction, and a rear skin material that covers the rear surface and peripheral portion of the rear body base.

As explained above, the present invention provides a chair with a suitable configuration in which at least the lumbar support, which can support the lower back of a seated person, can be repositioned vertically relative to the backrest, and can be attached and detached without having to attach or detach a fastening device.

FIG. 1 is a perspective view showing an embodiment of the present invention. FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. 4 is a plan view of the adjustment lever (reaction force adjustment lever) in the embodiment. 9(a) is a cross-sectional view taken along line AA in FIG. FIG. FIG. FIG. FIG. FIG. 3 is a cross-sectional view taken along line BB in FIG. 2. 3 is a cross-sectional view taken along line CC in FIG. 2 . Cross-sectional view taken along line D-D in FIG. FIG. FIG. FIG. FIG. FIG. 16 is an enlarged view of part E in FIG. Cross-sectional view taken along line FF in Figure 19. FIG. FIG. FIG. 31 is a view taken in the direction of the arrow G in FIG. 30 . FIG. FIG. FIG. FIG. 3 is a cross-sectional view taken along line JJ in FIG. 2. FIG. FIG. FIG. FIG. FIG. Cross-sectional view of line HH in Figure 41. Cross-sectional view of line II in Figure 41. Cross-sectional view taken along line L-L in FIG. FIG. 45 is a cross-sectional view for explaining the operation corresponding to FIG. 44 . FIG. 45 is a cross-sectional view for explaining the operation corresponding to FIG. 44 . FIG. FIG. FIG. 4 is a cross-sectional view taken along line K-K in FIG. 3. FIG. 4 is a perspective view of a support base main body in the embodiment. FIG. FIG. FIG. 4 is a right side view of the support base main body in the embodiment. FIG. 4 is a left side view of the support base main body in the embodiment. FIG. FIG. 4 is a bottom view of the support base main body in the embodiment. FIG. Cross-sectional view of line M-M in Figure 58. Cross-sectional view of line N-N in Figure 52. FIG. 2 is a perspective view showing a support base, a back support, and the like in the embodiment. FIG. FIG. 11 is a partially enlarged rear view showing a lumbar support according to another embodiment. FIG. FIG. FIG. FIG. FIG. Cross-sectional view of line O-O in Figure 67. Cross-sectional view of line P-P in Figure 68.

One embodiment of the present invention will be described below with reference to Figures 1 to 62.

In this embodiment, the present invention is applied to a swivel chair (hereafter simply referred to as "chair") suitable for use in an office or similar setting.

The chair comprises legs A, a support base B which is a support member supported rotatably on the legs A, a seat C placed on the support base B, a backrest E supported on the support base B via a back support D so that it can tilt backward, a lumbar support R attached to the backrest E, and a backrest surface extension member F and a hanger G which are options that can be selectively attached to the backrest E.

The chair in this embodiment is equipped with a so-called weight-sensing rocking mechanism V that moves the seat C upward and backward in response to the backward tilting of the backrest E.

<<Leg A>>
The leg A includes a plurality of leg blades a1 arranged radially, each having a caster a11 at its tip, and a leg support a2 erected at the base end of the leg blade a1.

The leg support a2 is configured to be extendable and retractable in the vertical direction. The leg support a2 is capable of supporting the support base B so that its vertical position can be changed by a gas spring (not shown).

<<Support Base B>>
The support base B is mainly composed of a support base main body 1 which is integrally formed from synthetic resin. The support base B is attached onto the legs A.

<Support base body 1>
The support base body 1 is integrally molded from synthetic resin. The support base body 1 has an internal storage space sp and is box-shaped with an open top. The support base body 1 is designed not to be covered by a cover body that is a separate member.

The support base body 1 not only performs the function of supporting the seat C and backrest E, but also exhibits design features that act as a cover without spoiling the aesthetic appearance.

At least a portion of the outer surface of the support base body 1, i.e., a portion of the downward surface 11s of the foundation bottom structure 11, the downward surface 12s of the inclined bottom wall 12, the downward surface 13s of the front bottom wall 13, and a portion of the outward surfaces 14s of the left and right side walls 14, are exposed to the outside and can be directly seen by the user.

The support base body 1 is provided with a foundation bottom structure 11 having a downward surface 11s attached to the leg support a2, an inclined bottom wall 12 having a downward surface 12s facing diagonally downward and rearward and extending diagonally downward and forward from the front end of the foundation bottom structure 11, a front bottom wall 13 having a downward surface 13s extending forward from the front end of the inclined bottom wall 12 and inclined to be positioned gradually upward as it moves forward, the foundation bottom structure 11, the inclined bottom wall 12, and left and right side walls 14 having outward surfaces 14s and extending upward from both left and right ends of the front bottom wall 13 in an upright position, and a front wall 15 having a forward surface 15s and in an upright position connecting the front ends of the left and right side walls 14.

The support base main body 1 is surrounded by a foundation bottom structure 11, an inclined bottom wall 12, a front bottom wall 13, left and right side walls 14, and a front wall 15, and is provided with a reaction force generating part HG, a bearing shaft d4 that engages with the reaction force generating part HG, a bearing shaft support member d3 that supports the bearing shaft d4, and an accommodation space sp that accommodates the lever base shaft part k3 of the reaction force adjustment lever K.

[Foundation bottom structure 11]
The foundation bottom structure 11 comprises a bottom wall portion 111 having a downward surface 11s, a boss portion 112 erected on the bottom wall portion 111, a rear curved wall 113 erected on the bottom wall portion 111, located behind the boss portion 112 and curved along the boss portion 112, a side upright wall 114 erected on the bottom wall portion 111, extending in the front-rear direction, and positioned between the boss portion 112 and the left and right side walls 14, a rear connecting wall 115 erected on the bottom wall portion 111 and extending in the front-rear direction connecting between the left-right central portion of the rear of the boss portion 112 and the left-right central portion of the rear curved wall 113, and a rear connecting wall 115 erected on the bottom wall portion 111 and extending in the front-rear direction connecting between the left-right central portion of the rear of the boss portion 112 and the left-right central portion of the rear curved wall 113. the side connecting wall 116 which is inclined in plan view and connects between the side portion of the boss portion 112 and the side upright wall 114; a front connecting wall 117 which is erected on the bottom wall portion 111 and connects between the front portion of the boss portion 112 and the side upright wall 114 and which is inclined in plan view; an outer connecting wall 118 which is erected on the bottom wall portion 111 and connects between the side upright wall 114 and the left and right side walls 14 and which is inclined in plan view; and an undershaft connecting portion 119 which is erected on the bottom wall portion 111 and connects between the side upright wall 114 and the left and right side walls 14 and is disposed below the main shaft jk1 inserted into the shaft hole 1b.

The shaft lower connecting portion 119 has a shaft holding recess 1e at its upper portion that constitutes a shaft holding portion JH capable of holding the main shaft jk1. The shaft holding portion JH will be described in detail later.

The foundation bottom structure 11 has a fitting hole 11a that is a connection part that penetrates the bottom wall part 111 and the boss part 112 and is externally fitted onto the leg support a2.

The rear end of the bottom wall 111 is provided with a mounting seat 111a for mounting a shock-absorbing attachment (not shown) that can engage with the rearward tilt degree setting lever H. The mounting members 11a are provided in pairs on the left and right sides of the partition wall 111d. The mounting seat 111a is provided with a hole 111b for mounting an attachment that penetrates in the vertical direction. A recess 111c is formed on the underside of the bottom wall 111 corresponding to the mounting seat 111a.

A nut portion n7 is provided on the boss portion 112 for mounting a gas spring operating mechanism (not shown) that can be operated by transmitting the operating force to the operating piece L arranged on the seat receptacle c1.

[Inclined bottom wall 12]
The inclined bottom wall 12 has a downward surface 12s facing diagonally downward and rearward, and is in a rearward inclined position extending diagonally downward and forward from the front end of the bottom wall portion 111 of the foundation bottom structure 11. A pair of left and right intermediate connecting walls 121 extending in the front-rear direction and connected to the front part of the foundation bottom structure 11 and the rear part of the front bottom wall 13 are provided on the inner surface of the inclined bottom wall 12.

The inclined bottom wall 12 has a side upright wall 122 extending in the front-rear direction and connected to the side upright wall 114 of the foundation bottom structure 11. In other words, the side upright wall 122 is provided on the inside of the left and right side walls 14.

[Front bottom wall 13]
The front bottom wall 13 has a downward surface 13s, extends forward from the front end of the inclined bottom wall 12, and is inclined so as to be positioned gradually higher as it moves forward.

The front bottom wall 13 is provided with a side upright wall 131 that is continuous with the side upright wall 122 of the inclined bottom wall 12 and extends in the front-rear direction. In other words, the side upright wall 131 is provided on the inside of the left and right side walls 14. In addition, the front bottom wall 13 is provided with a plurality of connecting walls 132 that connect the side upright wall 131 to the left and right side walls 14.

At the front of the front bottom wall 13, there are provided a number of bearings 133a, 133b, 133c that receive a number of retained shaft portions k31a, k31b, k31c provided on the lever base shaft portion k3 of the reaction force adjustment lever K, namely, the right bearing portion 133a on one side, the central bearing portion 133b, and the left bearing portion 133c on the other side.

The radius of curvature of the central bearing part 133b is set to be larger than the radius of curvature of the right bearing part 133a, and the radius of curvature of the left bearing part 133c is set to be larger than the radius of curvature of the central bearing part 133b.

The right bearing portion 133a and the left bearing portion 133c are each in an upwardly open position. The right bearing portion 133a and the left bearing portion 133c are provided on the upper portion of the side upright wall 131. The right bearing portion 133a and the left bearing portion 133c have a grease retaining groove 1j on the recessed surface.

The central bearing portion 133b is open toward the rear. The central bearing portion 133b is provided on the back support portion 13a that supports from the back side the reaction force adjustment lever K that is erected in the center of the front bottom wall 13 in the left-right direction and is constantly pressed by the reaction force generating portion HG. The central bearing portion 133b also has a grease retaining groove 1j on its recessed surface.

[Left and right side walls 14]
The left and right side walls 14 have outward surfaces 14a facing outward and are in an upright position extending upward from both left and right end portions of the bottom wall portion 111 of the foundation bottom structure 11, the inclined bottom wall 12, and the front bottom wall 13.

The left and right side walls 14 are provided with an axle hole 1b penetrating in the left-right direction at a position corresponding to the front of the bottom wall portion 111 of the foundation bottom structure 11 and capable of rotatably holding the main shaft jk1, a recess 1a provided on the periphery of the axle hole 1b and recessed in the thickness direction of the side wall 14, a long hole 1c penetrating in the left-right direction and capable of holding the front axle jk2 provided at the front end and capable of moving forward and backward to support the front part of the seat C, an annular protrusion 141 protruding outward so as to surround the opening edge of the axle hole 1b in a side view, and a lever insertion hole 142 provided on the rear side of the long hole 1c in the left side wall 14 and through which the reaction force adjustment lever K is inserted.

The shaft hole 1b is capable of rotatably supporting the main shaft jk1 that is installed between the left and right arms d1 of the back support D. In this embodiment, the shaft holes 1b provided in the left and right side walls 14 are parts that constitute the shaft holding portion JH for suitably holding the main shaft jk1 in the support base main body 1 made of synthetic resin.

That is, the shaft holding portion JH is composed of a shaft hole 1b, which is a through hole formed in the left and right side walls 14 corresponding to the size of the main shaft jk1, and a shaft holding recess 1e, which is connected to the inner side of the left and right side walls 14 and is provided on the upper part of the side upright wall 114 and the undershaft connecting portion 119 of the foundation bottom structure 11.

The shaft holding recess 1e is formed at a position corresponding to the shaft hole 1b. The shaft holding recess 1e is open upward. The shaft holding recess 1e has a continuous recessed surface 1f formed on the inner peripheral surface of the lower part of the shaft hole 1b.

The shaft holding recess 1e has a recessed shape so that it can rotatably hold the lower part of the main shaft jk1. The shaft holding recess 1e has multiple grease holding grooves 1g that extend in the front-rear direction along the recessed surface 1f and are spaced apart in the left-right direction.

The recess 1a is formed on the periphery of the shaft hole 1b, more specifically, below the shaft hole 1b. The recess 1a is provided approximately directly below the shaft hole 1b. The recess 1a is provided on the outer surface side of the left and right side walls 14. The recess 1a forms a space se that is approximately rectangular prism-shaped and open to the outside.

A resin portion JN is interposed between the recess 1a and the axial hole 1b. The vertical dimension w4 of the resin portion JN is set to be shorter than the diameter w2 of the axial hole 1b. The resin portion JN is composed of the lower part of the axial hole 1b in the left and right side walls 14 and the under-shaft connecting part 119 of the foundation bottom structure 11.

The inner dimension w1 in the front-to-rear direction of the recess 1a is set to be approximately equal to or shorter than the diameter w2 of the shaft hole 1b. The inner dimension w3 in the up-down direction of the recess 1a is set to be shorter than the diameter w2 of the shaft hole 1b. In a side view, the recess 1a is covered by the seat support c1 of the seat C.

The long hole 1c extends diagonally so that the lower end is located forward of the upper end in side view. A sleeve member SL made of a material that slides easily on the front axle jk2 is fitted into the long hole 1c. The front axle jk2 is supported by the long hole 1c via the sleeve member SL.

The annular protrusion 141 is configured so that the protruding end surface facing outward can contact the inner surfaces of the left and right arms d1 of the back support D.

[Front wall 15]
The front wall 15 has a forward surface s15 and is in an upright position connecting the front ends of the left and right side walls 14. The upper part of the front wall 15 is provided with a horizontally extending protruding wall 151 that is a rib extending in the left-right direction, and a plurality of vertically extending protruding walls 152 that are disposed on the horizontally extending protruding wall 151 and spaced apart in the left-right direction and extend in the up-down direction.

A reaction force generating part HG is disposed inside the support base main body 1, i.e., in the storage space sp, to generate a reaction force for the backrest E that can tilt backward. The reaction force generating part HG is disposed between a reaction force adjustment lever K pivotally supported on the support base B and a back support body D pivotally supported on the support base B and connected to the backrest E. The reaction force generating part HG is mainly composed of a coil spring HG1, which is a spring material.

A reaction force adjustment lever K, which is an adjustment lever for adjusting the reaction force of the backrest E, is rotatably supported on the support base B. The reaction force adjustment lever K is rotatably held between the support base main body 1 and a cover body Ba that covers the upper side of the lever base shaft part k3 of the reaction force adjustment lever K and is attached to the support base main body 1 by a screw v8. The screw v8, which is inserted through a screw insertion hole (not shown) provided in the cover body Ba, is screwed into a nut part n8 provided in the front bottom wall 13.

<<Reaction force adjustment lever K>>
The reaction force adjustment lever K is rotatably supported on the support base 1. The reaction force adjustment lever K is pivotally supported on the support base 1 so that its longitudinal axis is in the left-right direction. The reaction force adjustment lever K is rotated by the user's hand, and as the lever is rotated, the degree of compression of the coil spring HG, which is the spring material constituting the reaction force generating part HG, can be adjusted.

The reaction force adjustment lever K is provided with an operating part k1 at the tip, which is one end portion, and is gripped by the user to apply a rotational operating force; an intermediate connecting part k2, which is connected to the operating part k1 with its axis js aligned and has a shape in which the outer diameter dimension decreases with distance from the operating part k1; and a lever base shaft part k3, which is connected to the intermediate connecting part k2 with its axis js aligned and is pivotally supported on the support base main body 1, and has multiple, i.e., left, right, and center, retained shaft parts k31a, k31b, and k31c.

The operating part k1, intermediate connecting part k2, and lever base part k3 that make up the reaction force adjustment lever K are integrally formed from synthetic resin.

<Operation unit k1>
The operation unit k1 includes an operation unit body k11 having a generally cylindrical shape that is open to the outside, and a protrusion k12 that is a mark provided at an end of the operation unit body k11 and extends toward the center of the operation unit body k11. The protrusion k12 is a single protrusion provided from the inner peripheral surface of the operation unit body k11 toward the center of the operation unit body k11.

[Operation unit body k11]
The operation unit body k11 can form a substantially cylindrical space s1 inside. The operation unit body k11 is configured such that the outer peripheral surface of the tip portion k111 is gradually closer to the tip. In addition, the outer peripheral surface of the tip portion k111 of the operation unit body k11 is provided with a plurality of grooves k112 along the axis js to prevent finger slippage.

A mark recess k114 having a width dimension substantially equal to the thickness dimension of the protrusion k12 is formed on the outer peripheral surface of the tip portion k111 of the operating unit main body k11 corresponding to the protrusion k12. In other words, the recess k114 is provided on the outer peripheral surface of the tip portion k111 located directly behind the inner peripheral surface of the operating unit main body k11 from which the protrusion k12 protrudes.

[Protrusion k12]
The protrusion k12 protrudes from the inner peripheral surface of the operation unit main body k11 toward the axis js. The protrusion k12 is in the form of an upright wall extending along the longitudinal direction of the reaction force adjustment lever K. When viewed from the axis js direction, the protrusion k12 has a tip k121 which is a shaped portion that gradually narrows toward the axis js. In this embodiment, the shaped portion that gradually narrows is only present at the tip k121 of the protrusion k12. More specifically, the tip k121 of the protrusion k12 is in the form of a semicircular arc in a side view.

The protrusion k12 has an outward-facing end surface k122 that serves as a marker, located on the outward-facing edge of the operating unit body k11, i.e., outside the opening edge k113 of the operating unit body k11.

<Intermediate connecting portion k2>
The intermediate connecting portion k2 has an outer diameter that gradually decreases from the side having the operating portion k1 toward the side having the lever base portion k3. That is, the intermediate connecting portion k2 has a partial cone shape interposed between the operating portion k1 and the lever base portion k3.

Inside the intermediate connecting part k2, a roughly conical inner space s2 is formed, which is continuous with the cylindrical space s1 of the operating part main body k11. A protrusion k12 provided on the operating part main body k11 is connected to the inner peripheral surface of the tip side portion of the intermediate connecting part k2, i.e., the inner peripheral surface on the operating part k1 side.

<Lever base shaft portion k3>
The lever base shaft portion k3 is provided with a plurality of retained shaft portions k31a, k31b, k31c which are connected to the intermediate connecting portion k2 with their axis js aligned and journaled relative to the support base B, an engaging protrusion k32 which can engage with a protrusion for regulating the rotation range (not shown) provided on the cover body Ba of the support base B, and a cam portion k33 which can engage with a reaction force generating portion HG arranged inside the support base B.

The retained shaft portions k31a, k31b, and k31c are arranged in multiple numbers on the lever base shaft portion k3. Of the retained shaft portions k31a, k31b, and k31c arranged on the lever base shaft portion k3 at the left, right, and center, the diameter of the retained shaft portion k31a at the base end (right) is the smallest, and the diameter of the left retained shaft portion k31c, i.e., the retained shaft portion k31c at the tip side (operating portion k1 side), is set to be the largest.

In other words, the lever base shaft portion k3 is provided with multiple held shaft portions k31a, k31b, k31c of different diameters from the base end to the tip end, with the tip end having a larger diameter than the base end. More specifically, the diameter of the central held shaft portion k31b is set to be larger than the diameter of the right held shaft portion k31a, and the diameter of the left held shaft portion k31c is set to be larger than the diameter of the central held shaft portion k31b.

The engaging protrusions k32 are arranged at two positions on the left and right of the lever base shaft k3, spaced apart from each other. The engaging protrusions k32 can restrict the range of rotation around the axis js of the reaction force adjustment lever K, which receives the operating force from the user, by engaging with a protrusion for restricting the range of rotation (not shown) provided on the cover body Ba of the support base B.

The cam portion k31 is disposed at two locations on the left and right sides of the lever base shaft portion k3, spaced apart.

<<Seat C>>
The seat C includes a seat support c1 and a seat body c2 that is provided on the seat support c1 so that its front-rear position can be changed.

At the bottom of the seat support c1, an operating piece L is pivoted so that it can flap and move, acting on a gas spring (not shown) to expand and contract the leg support a2 in the vertical direction.

In this embodiment, the recess 1a provided on the outer surface of the support base main body 1 is covered by the seat support c1 in a side view. That is, a front lower extension wall c11 and left and right lower extension walls c12 that can cover the front and both sides of the support base main body 1 are formed at the lower part of the seat support c1. The left and right lower extension walls c12 of the seat support c1 cover the recess 1a of the support base main body 1 from the outside.

A cutout c121 is formed in the left lower extension wall c12 to avoid the reaction force adjustment lever K protruding from the support base main body 1.

The seat body c2 is configured to be able to slide forward and backward relative to the seat support c1.

<<Back support body D>>
The back support D is interposed between the support base B and the backrest E, and between the support base B and the seat C. The back support D has a rear shaft jk3 extending in the left-right direction that engages with a bearing portion (not shown) provided in the seat support c1 of the seat C. In other words, the back support D also functions as a seat support interposed to support the seat C on the support base B.

A rearward tilt setting lever H that can selectively set the rearward tilt degree of the backrest E is rotatably supported on the back support D.

The back support D is covered and concealed by a cover body I that is integrally formed from synthetic resin.

The back support D is equipped with a pair of left and right arms d1 pivoted to the support base body 1 of the support base B via the main shaft jk1, which is an upright plate-like shaft extending in the front-rear direction, a connecting member d2 in the shape of an upright plate connecting the rear parts of the pair of left and right arms d1, a rear shaft jk3 extending in the left-right direction supported at a position forward of the main shaft insertion hole d13 in the pair of left and right arms d1, a pair of left and right bearing shaft support members d3 arranged inside the pair of left and right arms d1, i.e., toward the center in the left-right direction, and with the upper part connected to the rear shaft jk3, and a bearing shaft d4 connected between the lower parts of the pair of left and right bearing shaft support members d3.

<Left and right arms d1>
The left and right arms d1 are made of metal. The left and right arms d1 are in the form of upright walls having left and right arm bodies d11 which are portions extending in the front-rear direction. The left and right arms d1 are disposed outside the left and right side walls 14 of the support base body d1.

The left and right arms d1 are provided with left and right arm bodies d11 that extend in the front-rear direction and can support the main shaft jk1 at their front ends, left and right front arm sections d12 that extend diagonally upward and forward from the front ends of the left and right arm bodies d11 and support the rear shaft jk3 that engages with the seat C at its upper end, and a main shaft insertion hole d13 that is provided between the left and right arm bodies d11 and the left and right front arm sections d12 and penetrates in the left-right direction and can hold the main shaft jk1.

[Left and right arm body d11]
The left and right arm bodies d11 extend in a substantially straight line in the front-rear direction. The rear portions of the left and right arm bodies d11 are connected by a connecting member d2. The rear ends of the left and right arms d11 protrude rearward beyond the connecting member d2, and the protruding portion d111 can be fitted into the back support body connecting portion 41 of the lower frame material 4 of the backrest E.

A shaft hole d112 is provided penetrating in the left-right direction in a portion of the left and right arm bodies d11 located forward of the portion where the connecting member d2 is attached. A rearward tilt setting lever H is rotatably supported in the shaft hole d112, which can selectively set one of the multiple types of rearward tilt degrees of the backrest 5.

[Left and right front arm parts d12]
The left and right front arm portions d12 are integrally extended obliquely upward and forward from the front ends of the left and right arm bodies d11. A rear shaft jk3 extending in the left-right direction and capable of engaging with the seat C is rigidly connected to the tip ends of the left and right front arm portions d12.

[Main shaft insertion hole d13]
The main shaft insertion hole d13, through which the main shaft jk1 is inserted, is provided at the front end portions of the left and right arm main bodies d11 and the base end portions of the left and right front arm portions d12, i.e., at the dogleg-shaped bent portions of the left and right arms d1.

<Connecting member d2>
The connecting member d2 is made of metal and has an upright plate shape extending in the left-right direction. The left and right ends of the connecting member d2 are rigidly connected to the inner parts of the left and right arms d1 by welding.

The connecting member d2 is provided with a nut portion n6 into which a screw v6 for attaching the backrest E is screwed. In other words, the rear portion of the back support D is provided with a backrest attachment portion da to which the backrest E is attached.

The backrest attachment portion da is composed of the rear portions of the left and right arms d1 and the connecting member d2 that connects the rear portions of the left and right arms d1, forming an H-shape in plan or bottom view.

<Rear axle jk3>
The rear axle jk3 extends in the left-right direction and is connected to the front ends of the left and right arms d1, i.e., the upper ends of the left and right front arm portions d12. The rear axle jk3 is located above the support base main body 1 and extends outward beyond both sides of the support base main body 1.

<Left and right bearing shaft support members d3>
The left and right bearing shaft support members d3 support the bearing shaft d4 pressed by the reaction force generating portion HG. The left and right bearing shaft support members d3 rigidly connect both ends of the bearing shaft d4 at their lower ends.

The left and right bearing shaft support members d3 are plate-shaped and arranged parallel to each other. The left and right bearing shaft support members d3 are arranged inside the left and right arms d1 and inside the side walls 14 of the support base main body 1. In other words, the left and right bearing shaft support members d3 are arranged closer to the center in the left-right direction than the left and right side walls 14 of the support base main body 1.

The upper parts of the left and right bearing shaft support members d3 are connected to the left-right center of the rear axle jk3. In addition, the rear parts of the left and right bearing shaft support members d3, which are located lower than the upper parts of the left and right bearing shaft support members d3, are provided with a main shaft insertion hole d31 through which the main shaft jk1 can be inserted. In other words, the rear parts of the left and right bearing shaft support members d3 are engaged with the main shaft jk1.

<Bearing shaft d4>
The receiving shaft d4 extends in the left-right direction and is disposed inside the support base main body 1. The receiving shaft d4 is connected to the reaction force generating part HG disposed in the support base B, and receives the biasing force generated by the reaction force generating part HG for biasing the backrest E in the direction of the normal posture. In this embodiment, the receiving shaft d4 is supported by the receiving shaft support member d3 so as to be located approximately directly below the rear axle jk3.

The back support body D described above has a bearing shaft d4 supported at the lower end of the left and right bearing shaft support members d3, and is connected at the upper end to the rear shaft jk3 and engaged at the rear end with the main shaft jk1. Therefore, the back support body D is configured so that the biasing force transmitted from the reaction force generating part HG to the bearing shaft d4 can be transmitted smoothly to the left and right arms d1 rotating around the main shaft jk1 via the left and right bearing shaft support members d3 and the rear shaft jk3 while avoiding interference with the support base main body 1 that opens upward.

<<Main shaft jk1>>
The spindle jk1 is held by the shaft holding portion JH of the support base main body 1. The spindle jk1 is equipped with a spindle body jk11 extending in the left-right direction, a flange portion jk12 that is integrally provided at one end of the spindle body jk11 and can engage with the outer surface of either the left or right arm d1 of the back support body D, and a retaining ring jk13 that is attached to the other end of the spindle body jk11 and can engage with the outer surface of the other of the left and right arms d1.

<<Backrest E>>
The backrest E comprises a backrest base, a back frame M, which has a screw insertion hole h6 and is attached to the backrest mounting portion da of the back support body D with a screw v2, a back frame cap T, which is a concealing member that is removably attached to the back frame M and can cover the storage space sd of the recess U formed in the lower frame material 4 of the back frame M, and a mesh-like tensioning member P that is stretched over the back frame M.

The backrest E has a backrest surface pm that supports the back of the seated person from behind, and is made of an upholstery member P that is mainly made of mesh fabric.

The chair of this embodiment is configured so that optional backrest surface extension members F and hangers G can be selectively attached to the upper frame material 3 of the backrest E.

In this embodiment of the chair, a lumbar support R is attached to the left and right side frame members 2 of the backrest E, which can support the lower back of the seated person from behind.

<Back frame M>
The back frame M comprises left and right side frame members 2 each having a tension member mounting groove mz opening outward, an upper frame member 3 having a tension member mounting groove mz opening upward and connecting the upper parts of the left and right side frame members 2, a lower frame member 4 connecting the lower parts of the left and right side frame members 2, and an intermediate connecting frame member 5 having a tension member mounting groove mz opening downward and connecting the left and right side frame members 2 together while forming an upper cavity sa between the upper frame member 3 and a lower cavity sb between the lower frame member 4.

The left and right side frame members 2, the upper frame member 3, and the lower frame member 4 are integrally molded from synthetic resin. The intermediate connecting frame member 5 is attached to the left and right side frame members 2 with screws v5.

The back frame M has an upper frame portion w1 that is made up of left and right side frame members 2, an upper frame member 3, and an intermediate connecting frame member 5, forming an upper cavity sa therein, and a lower frame portion w2 that is made up of left and right side frame members 2, a lower frame member 4, and an intermediate connecting frame member 5, forming a lower cavity sb therein.

In this embodiment, the backrest E is configured by tensioning a tensioning member P that can form the backrest surface pm to an upper frame portion w1 that is a frame portion provided on the back frame M.

The lower frame portion w2 is not provided with tensioning member P. In other words, a cavity sb is formed between the lower frame member 4 and the intermediate connecting frame member 5, which is a cross member, and is not provided with tensioning member P.

[Left and right side frame material 2]
The left and right side frame members 2 extend in the vertical direction. A tension member attachment groove mz is formed on the outer surface of each of the left and right side frame members 2, and continues from the upper end of the side frame member 2 to a height position that approximately corresponds to the lower edge of the intermediate connecting frame member 5. A tension member P is tensioned between the left and right side frame members 2 that extend in the vertical direction.

Each of the left and right side frame members 2 has an extension portion 23 that extends toward each other and connects the intermediate connecting frame member 5. The extension portion 23 has a base end portion 231 that extends inward like a column, and a tip end portion 232 that extends inward from the extended end of the base end portion 231, has an upright plate shape, and is set to have a shorter thickness dimension in the front-to-rear direction than the base end portion 231.

The front surface of the tip portion 232 is substantially flush with the front surface of the base portion 231. Meanwhile, the back surface of the tip portion 232 is located forward of the back surface of the base portion 321. In other words, a recessed portion 233 that is recessed forward is formed on the back surface side of the tip portion of the extension portion 23. The side end portion of the intermediate connecting frame material 5 is arranged in the recessed portion 233 when the intermediate connecting frame material 5 is attached.

The tip 232 has a screw insertion hole h5a that penetrates in the front-rear direction, and a rectangular recess 232a is formed on the front side for arranging a nut n5.

The left and right side frame members 2 each have an outer frame portion 21 with a tension member mounting groove mz that opens outward, and an inner frame portion 22 that is located inside the outer frame portion 21 and has a front portion located rearward of the front portion of the outer frame portion 21.

A tension member mounting groove mz is formed on the outer surface of the left and right side frame members 2, which continues from the upper end of the side frame member 2 to a height position that approximately corresponds to the upper edge of the base end portion 231 of the extension portion 23.

In addition, a step 2a is formed on the front surface of the left and right side frame members 2, extending inwardly and approximately horizontally from near the lower end of the upholstery member mounting groove mz. The step 2a is formed on the front surface at a height position that approximately corresponds to the upper edge of the extension portion 23 of the side frame member 2. The step 2a has a shape in which the lower side protrudes forward more than the upper side, and the step dimension approximately corresponds to the thickness dimension of the upholstery member P.

A lumbar support holder N is provided in the vertical middle of the left and right side frame members 2, more specifically, in the vertical middle of the inner frame portion 22 of the left and right side frame members 2, which is at a height position corresponding to the waist of a seated person, and is capable of holding the lumbar support R so that its vertical position can be changed.

The lumbar support holder N is provided at a portion of the left and right side frame members 2 that is bent forwardly in a convex manner in side view (a portion that is bent in a dogleg shape in side view).

The lumbar support holding portion N is capable of holding the held portions r22 provided on both the left and right ends of the lumbar support R. The lumbar support holding portion N is equipped with an accommodation groove 221 that extends in the vertical direction and is open to the front and that accommodates the upper protruding portion r221 and the lower protruding portion r222, which are multiple, i.e., two, protruding portions provided on the held portion r22 of the lumbar support R, and a holding member Q that is disposed in front of the accommodation groove 22 and has a front restricting portion q1 that can restrict the forward movement of the upper protruding portion r221 and the lower protruding portion r222.

The accommodation groove 221 is mainly formed by a rear groove forming wall 221a and a side groove forming wall 221b that engage with the retained portion r22. The accommodation groove 221 is provided with a rear groove forming wall 221a located on the rear side of the upper protruding portion r221 and the lower protruding portion r222, and a side groove forming wall 221b that extends forward from the inner side of the rear groove forming wall 221a and is located on the inner side of the upper protruding portion r221 and the lower protruding portion r222.

The front surface of the rear groove forming wall 221a forms an abutment portion that contacts the protruding ends of the upper protruding portion r221 and the lower protruding portion r222. The front surface, which is the abutment portion of the rear groove forming wall 221a, is inclined so that the inside is located behind the outside.

The inner surface of the side groove forming wall 221b, i.e., the surface facing the front side of the rear groove forming wall 221a, forms an abutment portion that contacts the inner portions of the upper protruding portion r221 and the lower protruding portion r222. The side groove forming wall 221b that can form the storage groove 221 is provided with an upper notch 221c and a lower notch 221d that are notches that allow the upper protruding portion r221 and the lower protruding portion r222 to pass through when attaching or detaching the lumbar support R to the backrest E.

That is, the side groove forming wall 221b has an upper notch 221c through which the upper protruding portion r221 can pass when the lumbar support R is attached to and detached from the backrest E, and a lower notch 221d through which the lower protruding portion r222 can pass. The upper notch 221c and the lower notch 221d are formed spaced apart above and below the side groove forming wall 221b. Also, the upper notch 221c and the lower notch 221d are provided in the front half of the side groove forming wall 221b.

The shape of the upper cutout 221c is set to correspond to the upper protruding portion r221 of the lumbar support R so that the upper protruding portion r221 can pass through the upper cutout 221c. In addition, a protrusion 221e is provided in the center of the upper cutout 221c in the vertical direction so as to correspond to the shape of the upper protruding portion r221.

The shape of the lower cutout 221d is set to correspond to the lower protruding portion r222 of the lumbar support R so that the lower protruding portion r222 can pass through. Note that the shape of the upper protruding portion r221 and the shape of the lower protruding portion r222 of the lumbar support R are different.

By making the shape of the upper notch 221c corresponding to the upper protruding portion r221 and the shape of the lower notch 221d corresponding to the lower protruding portion r222 different, the user can easily grasp the up and down positions of the lumbar support R. In other words, the chair of this embodiment is designed to prevent the user from attaching the lumbar support R to the backrest E with the wrong up and down.

The retaining member Q is made of synthetic resin and is constructed from a separate member from the left and right side frame members 2. In other words, the retaining member Q is separate from the left and right side frame members 2. The retaining member Q is attached to each of the left and right side frame members 2. The retaining member Q is attached to the inner frame portion 22 of the left and right side frame members 2 via screws v3.

The retaining member Q extends in the vertical direction and includes a front restricting portion q1 that is disposed in front of the accommodation groove 221 and can restrict the forward movement of the upper protruding portion r221 and the lower protruding portion r222 of the lumbar support R by abutting against the upper protruding portion r221 and the lower protruding portion r222, an attachment portion q2 that is connected to the upper and lower ends of the front restricting portion q1 and has a screw insertion hole h3 that penetrates in the front-rear direction, and a positioning wall q3 that extends from the outer side of the front restricting portion q1 toward the rear, i.e., toward the inner frame portion 22, and is disposed between the accommodation groove 221 and the outer frame portion 21.

The front restricting portion q1 is shaped like a rail extending in the vertical direction. The front restricting portion q1 is capable of clamping the upper protruding portion r221 and the lower protruding portion r222 in the front-rear direction by cooperating with the inner groove forming wall 221a that can form the accommodation groove 221.

Between the front restricting portion q1 of the retaining member Q and the side groove forming wall 221 of the accommodation groove 221, a communication space sc extending in the vertical direction is formed through which the retained portions r22 of the left and right arm materials r2 of the lumbar support R, which have an upper protruding portion r221, a lower protruding portion r222, and a protruding portion 220 at their tips, can communicate.

In other words, the retaining member Q cooperates with the left and right side frame members 2 to clamp and hold the upper protruding portion r221 and the lower protruding portion r222. As a result, the lumbar support R is clamped in the front-to-rear direction between the forward surfaces of the left and right side frame members 2 and the rearward surface of the retaining member Q, and can be appropriately held in a predetermined vertical position within the accommodation groove 221 without sliding downward due to gravity.

The mounting portion q2 has a screw insertion hole h3 for mounting the retaining member Q to the inner frame portion 22 of the left and right side frame members 2. The mounting portion q2 also has an external fitting wall q21 protruding therefrom that can be fitted onto the peripheral edge of the nut portion n3 protruding from the inner frame portion 22 of the left and right side frame members 2.

The retaining member Q is attached to the inner frame portion 22 of the left and right side frame members 2 by screwing the screw v3 inserted through the screw insertion hole h3 into the nut portion n3 provided on the left and right side frame members 2.

[Upper frame material 3]
The upper frame material 3 extends in the left-right direction. The upper frame material 3 has an outer frame portion 31 in which a tension member mounting groove mz that opens upward for mounting a tension member P is formed, and an inner frame portion 32 disposed below the outer frame portion 31. The upper frame material 3 is provided with a nut holding recess nt in which a nut member J for mounting an option can be held, as will be described in detail later.

The outer frame portion 31 constitutes the upper portion of the upper frame material 3. The front surface of the outer frame portion 31 forms the portion that is attached to the back surface of the tension member P, i.e., the portion that backs the tension member P.

The inner frame portion 32 constitutes the lower portion of the upper frame material 3. The inner frame portion 32 is located inside the outer frame portion 31. In other words, the inner frame portion 32 is located in a position that is covered by the tension member P when viewed from the front.

The inner frame portion 32 includes a hanging wall 321 that hangs down from the rear of the outer frame portion 31, a lower end wall 322 that extends forward from the lower end of the hanging wall 321, and a number of connecting walls 323 that form upright walls connecting the lower end wall 322 to the outer frame portion 31 and the lower end wall 322 to the hanging wall 321.

The back surface of the hanging wall 321 is generally flush with the back surface of the outer frame portion 31. The bottom end wall 322 is provided at a distance in the up-down direction from the outer frame portion 31. The connecting walls 323 are provided to increase the connection strength between the bottom end wall 322 and the outer frame portion 31, and are provided in multiples at regular intervals in the left-right direction.

The inner frame portion 32 is provided with a nut holding recess nt that is formed with an upper opening portion kh1 that opens upward, a lower opening portion kh2 that opens downward, and a front opening portion kh3 that opens forward and can hold a nut member J. The nut holding recess nt is provided in multiple locations on the inner frame portion 32.

The nut holding recess nt is provided in the lower end wall 322 of the inner frame portion 32. The nut holding recess nt has left and right standing wall portions nt1 and a rear standing wall portion nt2 that connects the rear portions of the left and right standing wall portions nt1. The nut holding recess nt is generally U-shaped and open to the front when viewed from the bottom.

The nut holding recess nt is formed by the left and right upright wall portions nt1 and the rear upright wall portion nt2, which defines an upper opening portion kh1 that opens upward, a lower opening portion kh2 that opens downward, and a front opening portion kh3 that opens forward.

The nut holding recess nt also forms a portion that can form the upper open portion kh1 with the upper edges of the left and right upright wall portions nt1 and the upper edge of the rear upright wall portion nt2, and also forms a flange engaging portion nt3 that can engage with the underside of the flange portion j2 of the nut member J.

A gap sk is formed between the nut holding recess nt and the outer frame portion 31, allowing the flange portion j2 of the nut member J to be accommodated.

In this embodiment, the inner frame portion 32 is provided with four nut holding recesses nt spaced apart in the left-right direction. A pair of nut holding recesses nt located on both the left and right outer sides are used when attaching a backrest surface extension member F for extending the backrest surface pm, and a pair of nut holding recesses nt located on both the left and right inner sides are used when attaching a hanger G for hanging clothes.

The nut member J held in the nut holding recess nt is made of metal. The nut member J has a boss portion j1 that is housed in the enclosed space of the nut holding recess nt and has a thread groove j11 on its inner circumferential surface, and a flange portion j2 that is connected to the boss portion j1 and can engage with a flange portion engagement portion nt3, the lower surface of which forms the upper open portion kh1.

The nut member J is generally T-shaped. That is, the flange portion j2 extends longitudinally outward in the left-right direction from the upper end of the generally cylindrical boss portion j1.

The method of holding the nut member J in the nut holding recess nt provided in the backrest E and attaching the optional backrest surface extension member F and optional hanger G will be described in detail later.

[Bottom frame material 4]
The lower frame member 4 has a portion that connects the lower portions of the left and right side frame members 2 and is connected to the back support member D. The lower frame member 4 is provided with a back support member connecting portion 41 that is recessed and open forward, for fitting externally to the backrest mounting portion da provided on the back support member D and connecting the backrest mounting portion da.

The back side of the lower frame material 4 is provided with a recess U in which an accommodation space sd is formed that can accommodate the head v61 of the screw v6 for connecting the back frame M to the back support D. The recess U is recessed so that the accommodation space sd can be formed inside while opening to the rear. In other words, the recess U has an opening uk that is open to the rear and has the accommodation space sd formed therein.

The lower frame material 4 is provided with screw insertion holes h6 through which the screws v6 are inserted, penetrating in the front-to-rear direction. The screw insertion holes h6 are provided in pairs on the left and right. The screw insertion holes h6 are provided so as to be able to communicate between the recess U that opens to the rear and the back support connecting portion 41 that opens to the front.

The recess U is provided with a screw engagement wall u1, which is a rear wall in which the screw insertion hole h6 is drilled and into which the head 61 of the screw v6 can engage; an upright wall u2, which is a front wall located behind the screw engagement wall u1 and in front of the opening uk; a peripheral wall u3 that extends in the front-to-rear direction and whose inner side faces the storage space sd; and an intermediate wall u4 that extends in the front-to-rear direction and has a surface facing the storage space sd and connects the outer end of the upright wall u2 and the inner end of the screw engagement wall u1.

The screw engagement walls u1 are provided in pairs on the left and right. When viewed from the rear, the screw engagement walls u1 are circular, with a screw insertion hole h6 formed in the center. The opposite surface of the screw engagement wall u1, that is, the forward surface, abuts against the rear surface of the connecting member d2 of the back support body D. In other words, the screw engagement wall u1 also serves as an engagement wall with the connecting member d2 of the back support body D.

The standing wall u2 is provided inside the screw engagement walls u1 provided on the left and right sides when viewed from the rear. The standing wall u2 is elongated in the left-right direction and is disposed in a position that is approximately parallel to the screw engagement walls u1. The standing wall u2 has a window hole u21 that serves as an engagement portion with which the locking protrusion t31 formed on the fall-off prevention protrusion t3 of the back frame cap T can engage. The window holes u21 are approximately rectangular and are provided in pairs on the left and right sides.

The peripheral wall u3 has an inner peripheral surface u31 that faces in a direction substantially perpendicular to the front-to-rear direction, and an opening uk is formed by the inner peripheral surface u31 at the rear end of the peripheral wall u3. In other words, the opening uk does not have a portion that can restrict the cap body t1 of the rear frame cap T from advancing too far inward.

In other words, the opening uk has a shape that allows the cap body t1 to move toward the back, and does not have any parts that could prevent movement in the depth direction, such as steps, protrusions, ribs, etc.

<Back frame cap T>
The back frame cap T is removably attached to the lower frame material 4 and can cover the storage space sd of the recess U. In this embodiment, the screw v6 can be confirmed based on the relative position of the back frame cap T with respect to the lower frame material 4.

The back frame cap T is provided with a cap body t1, which is a concealing member body disposed in the opening uk of the recess U and capable of hiding the storage space sd from the outside, a screw head abutment protrusion t2 protruding from the cap body t1 and having a tip t21 capable of abutting against the head v61 of the screw v6, and a detachment prevention protrusion t3 protruding from the cap body t1 and engaging with the recess U to prevent the back frame cap T from coming off the back frame M.

[Cap body t1]
The cap body t1 is in the form of an upright plate extending in the left-right direction. That is, the cap body t1 has a flat outer surface 4a and is in the form of a horizontally elongated plate that is in an upright position as a whole. The left and right side portions of the cap body t1 are formed in a semicircular shape when viewed from behind.

[Screw head contact protrusion t2]
The screw head abutment protrusions t2 are provided so as to protrude forward from the cap body t1. The screw head abutment protrusions t2 are provided in pairs on the left and right in correspondence with the left and right screw insertion holes h6. The screw head abutment protrusions t2 are provided so as to protrude forward from both the left and right ends of the cap body t1.

The protruding dimension of the screw head abutment protrusion t2 is set to a length such that when the screw v6 has been properly screwed into the nut portion n6 of the back support D (i.e., when the head v61 of the screw v6 abuts against the screw engagement wall u1 and cannot proceed any further forward), the outer surface t11 of the cap body t1 is approximately flush with the outer surface 4a of the peripheral portion of the recess U when the tip t21 engages with the head v61.

[Anti-fall protrusion t3]
The retaining projections t3 are provided forward from the cap body t1. The retaining projections t3 are provided in pairs on the left and right. The pair of retaining projections t3 are disposed between the pair of screw head abutment projections t2 provided on the left and right.

The anti-removal protrusion t3 is generally arrow-shaped in side view. The anti-removal protrusion t3 has a locking protrusion t31 that protrudes upward and downward near its tip. The anti-removal protrusion t3 is set to a size that allows the part other than the locking protrusion t31 to pass through the window hole u21 in the front-rear direction.

The locking projection t31 of the anti-detachment projection t3 engages with a window hole u21 provided in the upright wall u2 of the recess U, restricting only the rearward movement of the back frame cap T. When the locking projection t31 engages with the window hole u21 and restricts rearward movement, the outer surface t11 of the cap body t1 is substantially flush with the outer surface 4a of the peripheral portion of the recess U.

[Verification function for screw v6 based on the position of the back frame cap T]
In the chair of this embodiment, confirmation regarding the screw v6 can be performed based on the relative position of the back frame cap T with respect to the lower frame material 4.

More specifically, it is configured to be able to check whether the screw v6 is properly screwed in as intended and whether any screw v6 has been left in place based on the relative position between the outer surface t11 of the back frame cap T and the outer surface 4a of the lower frame material 4.

The back frame cap T is configured so that the outer surface t11 of the cap body t1 is approximately flush with the outer surface 4a of the peripheral portion of the recess U only when the screw v6 is inserted into the screw insertion hole h6 and has completed screwing into the nut portion n6 provided on the back support D, i.e., when the screw v6 is properly attached.

[If screw v6 is installed correctly]
As shown in FIG. 44, the tip t21 of the screw head abutment protrusion t2 abuts against the head v61 of the screw v6, so that the rear frame cap T is restricted from moving further forward.

In addition, the rear frame cap T is restricted from moving backward because the locking projection t31 of the anti-detachment projection t3 engages with the window hole u21 of the upright wall u2 in the recess U.

In this state, the outer surface t11 of the cap body t1 in the back frame cap T is substantially flush with the outer surface 4a of the peripheral portion of the recess U, so the assembly worker can see that the outer surfaces t11, 4a are substantially flush and can confirm that the backrest E is properly attached to the back support body D using the screw v6.

[If the screw v6 is not properly threaded (the screwing is not yet complete)]
As shown in FIG. 45, the tip t21 of the screw head abutment protrusion t2 abuts against the head v61 of the screw v6, so that the rear frame cap T is restricted from moving further forward.

However, in the example shown in Figure 45, the screw v6 has not yet fully engaged (the screw v6 is not fully tightened/screwed loosely), so in this state the outer surface t11 of the cap body t1 in the back frame cap T is positioned outside the outer surface 4a of the peripheral portion of the recess U.

As a result, the assembly worker can see that the positions of the outer surfaces t11, 4a are not approximately flush and can confirm that the backrest E is not properly screwed to the back support D.

[If screw v6 is not installed]
As shown in Figure 46, after the back support body connecting portion 41 of the backrest E is temporarily supported by being externally fitted onto the protruding portion d111 constituting the backrest mounting portion da of the back support body D, it is possible that the worker will forget to screw in the screw v6.

In this case, since the head v61 of the screw v6 is not disposed in the recess U, the tip t21 of the screw head abutment protrusion t2 of the back frame cap T cannot abut against the head v61 of the screw v6. Furthermore, the back frame cap T continues to move forward as the locking projection t31 of the anti-detachment protrusion t3 passes through the window hole u21 of the upright wall u2 in the recess U.

At this time, the locking projection t31 of the anti-detachment projection t3 can only engage with the window hole u21 at a specified position to restrict only rearward movement, but cannot restrict forward movement.

As shown in FIG. 46, if the screw v6 for attaching the backrest E to the back support D is not inserted into the screw insertion hole h6, the back frame cap T will go deep into the recess U so that the outer surface t11 of the cap body t1 is not substantially flush with the outer surface 4a of the peripheral portion of the recess U.

As the retaining projection t3 continues to advance forward through the window hole u21, the tip t21 of the screw head abutment projection t2 of the back frame cap T hits the screw engagement wall u1, which is the rear wall that can form the recess U, and finally, movement backward in the back frame cap T is restricted.

At least in this state, the back frame cap T is configured so that the outer surface t11 of the cap body t1 is located behind the outer surface 4a of the peripheral portion of the recess U, so that the assembly worker can see that the positions of the outer surfaces t11 and 4a are not approximately flush and can confirm that the backrest E is not properly screwed to the back support body D (the screw v6 is missing).

[Intermediate connecting frame material 5]
The intermediate connecting frame member 5, which is a cross member, extends in the left-right direction. The intermediate connecting frame member 5 is installed between the portions of the left and right side frame members 2 that are tilted forward when viewed from the side. The intermediate connecting frame member 5 is separate from the other frame members that make up the back frame M, i.e., the left and right side frame members 2, the upper frame member 3, and the lower frame member 4.

In this embodiment, the intermediate connecting frame member 5 is configured to be detachably attached to the left and right side frame members 2 via screws v5. Both left and right ends of the intermediate connecting frame member 5 are screwed to the left and right side frame members 2, respectively. The intermediate connecting frame member 5 has a curved shape that is convex toward the rear in a plan view. The intermediate connecting frame member 5 is formed with a tension member mounting groove mz that opens downward.

The intermediate connecting frame member 5 is capable of supporting the lower part of the tension member P. The intermediate connecting frame member 5 is equipped with an intermediate connecting frame member main body 51 in the form of an upright plate having a tension member mounting groove 5 that is open downward, and mounting parts 52 that are arranged at both ends of the intermediate connecting frame member main body 51 and have screw insertion holes h5b that penetrate in the front-to-rear direction.

The intermediate connecting frame member body 51 that constitutes the intermediate connecting frame member 5 has a tension member attachment groove mz that is open downward. The lower end portion pe of the tension member P is attached to the tension member attachment groove mz.

The left and right mounting parts 52 have screw insertion holes h5b formed therein, and are attached to the extension parts 23 provided on the left and right side frame members 2 with screws v5. In other words, the intermediate connecting frame member 5 is attached to the left and right side frame members 2 by screwing the screws v5 inserted through the screw insertion holes h5b and h5a into the nuts n5 of the extension parts 23.

The left and right mounting parts 52 are set to have a shorter thickness dimension in the front-to-rear direction than the intermediate connecting frame body 51. The rear surface of the mounting parts 52 is substantially flush with the rear surface of the intermediate connecting frame body 51. Meanwhile, the front surface of the mounting parts 52 is located behind the front surface of the intermediate connecting frame body 51. In other words, a recessed portion 53 recessed toward the rear is formed on the front side of both ends of the intermediate connecting frame 5. The tip portion 232 of the extension portion 23 is arranged in the recessed portion 53.

In this embodiment, as shown in FIG. 50, the tension member P is wrapped around the intermediate connecting frame member 5 so as to cover the back surface of the intermediate connecting frame member 5. More specifically, the tension member P is wrapped around the intermediate connecting frame member 5 from the lower end portion pe in the order of back surface, top surface, front surface, bottom surface, and back surface. Therefore, the tension member P is arranged in two layers, front and back, on the back surface side of the intermediate connecting frame member 5.

<Stretching member P>
The upholstery member P is mainly made of a mesh-like fabric capable of forming the backrest surface pm.

The tension member P is attached to the tension member attachment groove mz provided on the upper frame portion w1 of the back frame M at its peripheral portion. The tension member P is stretched over the front side of the upper frame portion w1 of the back frame M.

The end portion pe of the tension member P attached to the upper frame portion w1 has an inserted member ps sewn to it, which is inserted together with the tension member P into the tension member attachment groove mz. The inserted member ps of the end portion pe is of a size that allows it to be pressed into the tension member attachment groove mz of the upper frame portion w1 during assembly, and is, for example, a strip-shaped member made of synthetic resin.

The end portion pe of the lower edge of the tension member P is to be attached to the tension member attachment groove mz of the intermediate connecting frame material 5. As shown in FIG. 50, the tension member P is wrapped around the intermediate connecting frame material 5 from the lower end portion pe side in the order of back surface, top surface, front surface, bottom surface, and back surface.

An example of how to attach the intermediate connecting frame material 5 with the tension member P wrapped around it to the extension parts 23 of the left and right side frame materials 2 is as follows.

First, the part of the tension member P that is wrapped around the mounting part 52 is temporarily pressed toward the intermediate connecting frame body 51 and moved, and the mounting part 52 exposed to the outside is fastened to the extension part 23 with the screw v5.

Next, the portion that was temporarily pressed and moved toward the intermediate connecting frame member main body 51 is shifted and moved to a position where the mounting portion 52 and the extension portion 23 can be wound. As a result, the screw v5 for attaching the intermediate connecting frame member 5 to the left and right side frame members 2 is doubly covered by the tension member P when viewed from behind, providing a favorable appearance.

Then, the upper and left and right end portions pe of the tension member P are attached to the tension member attachment grooves mz of the upper frame material 3 and the left and right side frame materials 2, completing the installation of the tension member P to the back frame M.

The above-mentioned installation procedure is merely one example. For example, the tension member P may be wrapped around the intermediate connecting frame material 5 while the intermediate connecting frame material 5 is screwed to the left and right side frame materials 2.

<<Lumbar Support R>>
The lumbar support R is installed between the left and right side frame members 2. The lumbar support R is located behind the tension member P and is capable of supporting the lower back of a seated person. The lumbar support R is vertically changeable relative to the left and right side frame members 2 of the backrest E, and is provided detachably without the need to attach or detach fasteners such as screws.

In other words, in this embodiment, the lumbar support R can be attached to the backrest E after the fact or removed from the backrest E by temporarily bending the lumbar support R and inserting or removing the held portion r22 into or from the lumbar support holding portion N without using fasteners such as screws.

The lumbar support R comprises a lumbar support body r1 extending in the left-right direction, and left and right arm members r2 supported by the lumbar support body r1. The left and right arm members r2 are supported so as to be movable in the left-right direction relative to the lumbar support body r1.

<Lumbar support body r1>
The lumbar support main body r1 comprises a front main body member r11 and a rear main body member r12 which is approximately the same size as the front main body member r11 and is attached to the rear side of the front main body member r11.

[Front body member r11]
The front main body member r11 includes a front main body base r111 made of synthetic resin in the shape of a plate extending in the left-right direction, and a front cover material r112 that covers the front surface and peripheral edge portion of the front main body base r111.

The front body base r111 can be temporarily deflected in the thickness direction. The front body base r111 has an overall horizontally elongated plate shape in an upright position. Both left and right side portions of the front body base r111 are formed in a semicircular shape when viewed from the front.

The front body base r111 is provided with claw receiving portions r113 at multiple locations that receive the engagement claws r123 provided on the rear body base r121 of the rear body member r12.

A triangular prism-shaped positioning protrusion r114 protrudes rearward from the center of the front body base r111 in the left-right and up-down directions and can fit into a fitting recess r124 provided in the rear body base r121 of the rear body member r12.

On the left and right sides of the front body base r111, there are provided outwardly U-shaped guide walls r115 that engage with the outer edges of the arm bases r21 that constitute the left and right arm materials r2, respectively, and can guide the left and right movement of the left and right arm materials r2 relative to the lumbar support body r1.

[Rear body member r12]
The rear main body member r12 includes a rear main body base r121 made of synthetic resin in the shape of a plate extending in the left-right direction, and a rear skin material r122 that covers the rear surface and peripheral edge portion of the rear main body base r121.

The rear body base r121 is provided with engagement claws r123 at multiple locations that can engage with the claw receiving portions r113 provided on the front body base r111 of the front body member r11.

A fitting recess r124 is formed in the center of the rear body base r121 in the left-right and up-down directions, into which the triangular prism-shaped positioning protrusion r114 provided on the front body base r111 of the front body member r11 can fit.

On the left and right sides of the rear body base r121, there are provided outwardly U-shaped guide walls r125 that engage with the outer edges of the arm bases r21 constituting the left and right arm materials r2, respectively, and can guide the left and right movement of the left and right arm materials r2 relative to the lumbar support body r1.

In the inner area surrounded by the guide wall r125 of the rear body base r121, an upper convex portion r126 and a lower convex portion r127, which are the first engagement portions, are disposed toward the front, i.e., toward the front body base r111.

The upper convex portion r126 and the lower convex portion r127 are capable of engaging with the upper engaging hole r213 and the lower engaging hole r214, which are horizontally elongated holes and are second engaging portions provided on the inner plate-like portion r211 of the left and right arm members r2.

<Left and right arm material r2>
The left and right arm materials r2 are sandwiched between a front main body member r11 and a rear main body member r12. The left and right arm materials r2 have at their outer ends held portions r22 that are held by a lumbar support holding portion N provided on the backrest E. The left and right arm materials r2 are each integrally formed from a synthetic resin.

The left and right arm members r2 each have an arm base r21 having a rectangular plate-like portion extending in the left-right direction, and a held portion r22 that is connected to the outer end of the arm base r21 and is held by the lumbar support holding portion N of the backrest E.

The arm base r21 and the held portion r22 that make up the left arm material r2 are integrally formed from synthetic resin, and the arm base r21 and the held portion r22 that make up the right arm material r2 are integrally formed from synthetic resin.

[Arm base r21]
The arm base r21 has an inner plate-like portion r211 which is rectangular extending in the left-right direction and is located within the lumbar support main body r1, and an outer plate-like portion r212 which is plate-like and has a portion extending diagonally forward and outward from the outer edge of the inner plate-like portion r211.

The inner plate-like portion r211 has a generally rectangular shape with the upper and lower edges generally parallel to each other. The upper and lower parts of the inner end of the inner plate-like portion r211 are provided with an upper engagement hole r213 and a lower engagement hole r214, which are long hole-shaped second engagement parts extending in the left-right direction. In addition, the center of the inner plate-like portion r211 in the left-right direction is provided with an elongated interference avoidance hole r215 for avoiding the boss portion r128 having a screw insertion hole h4, and a rectangular interference avoidance hole r216 for avoiding the engagement claw r123 and claw receiver r113, which are the connecting mechanism for connecting the front main body member r11 and the rear main body member r12.

The upper convex portion r126 and the lower convex portion r127, which are the first engagement portions provided on the lumbar support main body r1, engage with the upper engagement hole r213 and the lower engagement hole r214, which are the second engagement portions provided on the inner plate-like portion r211 of the left and right arm materials r2, so that the left and right arm materials r2 are configured to be movable in the left and right direction relative to the lumbar support main body r1. The upper engagement hole r213 and the lower engagement hole r214 are set to a dimension longer in the width direction than the upper convex portion r126 and the lower convex portion r127.

The outer plate-like portion r212 is disposed outside the lumbar support body r1. The outer plate-like portion r212 includes an inclined extending plate portion r217 that extends diagonally forward and outward from the outer edge of the inner plate-like portion r211, and a horizontal extending plate portion r218 that extends outward from the extending end of the inclined extending plate portion r217.

[Holded portion r22]
The held portion r22 has an upper protruding portion r221 and a lower protruding portion r222 that protrude rearward and are arranged with a gap between them in the vertical direction.

The upper protruding portion r221 and the lower protruding portion r222 protrude rearward from the outer edge of the outer plate-like portion r212 that constitutes the arm base r21, i.e., the outer end of the horizontally extending plate portion r218 of the outer plate-like portion r212. The upper protruding portion r221 and the lower protruding portion r222 bulge outwardly and obliquely rearward from the outer end portion of the arm base r21.

The front ends of the upper protruding portion r221 and the lower protruding portion r222 are provided with forward-facing engagement surfaces r223, r227 that face forward and serve as front engagement portions that can engage with the front restriction portion q1 of the holding member Q that constitutes the lumbar support holding portion N.

The rear ends of the upper protruding portion r221 and the lower protruding portion r222 are provided with rearward engaging surfaces r224, r228 that face rearward and can engage with the groove forming wall 221a at the back of the accommodation groove 221 that constitutes the lumbar support holding portion N.

The inner ends of the upper protruding portion r221 and the lower protruding portion r222 are provided with lateral engagement surfaces r225, r226 that face inward and serve as side engagement portions that can engage with the groove forming wall 221b on the side of the accommodation groove 221 that constitutes the lumbar support holding portion N.

In this embodiment, the shape of the upper protruding portion r221 is set to be different from the shape of the lower protruding portion r222. More specifically, the upper protruding portion r221 has a notch r226 in the vertical middle of the rear end portion, which is the protruding end portion, but the lower protruding portion r222 does not have a similar notch. In addition, the vertical dimension of the upper protruding portion r221 is set to be shorter than the vertical dimension of the lower protruding portion r222.

The chair of this embodiment is designed to prevent a user from attaching the lumbar support R to the backrest E with the wrong top and bottom. The upper cutout 221c formed in the accommodation groove 221 of the lumbar support holding portion N corresponds to the shape of the upper protruding portion r221 of the lumbar support R. In other words, the upper cutout 221c is provided with a protrusion 221e that can pass through the cutout r226 of the upper protruding portion r221.

The supported portion r22 of the lumbar support R is provided with a eaves-like protruding portion r220 that connects the upper protruding portion r221 and the lower protruding portion r222 and protrudes outward from the outer end of the arm base r21 (i.e., the outer end of the horizontal extension portion r218 in the outer plate portion r212).

<<Backrest surface expansion member F>>
The backrest surface extension member F is for providing an extended backrest surface fm as a contact surface that can contact the user on the backrest surface pm formed by the backrest E. The backrest surface extension member F in this embodiment is called a "shoulder support" because the user's shoulders can mainly contact the extended backrest surface fm.

The backrest surface extension member F comprises a pad body f1, the front of which is an extended backrest surface fm that can come into contact with the user, and a base body f2 that can support the pad body f1.

The backrest surface extension member F has an upper frame material placement recess fu between the lower part of the base body f2 and the lower end of the pad body f1, which is open to the front and both sides.

The backrest surface extension member F is provided with a movement restriction portion ks located on the rear side of the upper frame material 3 in the backrest E at a position facing the upper frame material arrangement recess fu, and capable of restricting forward movement by engaging with the rear portion of the upper frame material 3.

<Pad body f1>
The pad body f1 comprises a pad body main body f3 attached to a pad body attachment portion f6 provided on the base body f2, and a front cover material f4 covering the front surface and peripheral edge portion of the pad body main body f3.

The pad body f1 has a generally rectangular shape with its long sides extending in the left-right direction when viewed from the front. The pad body f1 has a generally symmetrical shape when viewed from the front. The edges of both the left and right sides of the pad body f1 are gently curved so as to convex outward when viewed from the front. The extended backrest surface fm, which is the front surface of the pad body f1, is set to be generally flush with the backrest surface pm formed by the upholstery member P.

The vertical dimension of the pad body f1 is shorter than the vertical dimension of the base body f2. The position of the upper edge of the pad body f1 is approximately aligned with the position of the upper edge of the base body f2. The shape of the side edge of the pad body f1 in a front view is approximately aligned with the shape of the side edge at the same height position of the base body f2. The lower edge of the pad body f1 is set at a position that approximately abuts against the upper frame material 3.

[Pad body f3]
The pad body main body f3 includes a pad base f31 formed of synthetic resin in the shape of a generally upright plate, and a cushion f32 made of urethane foam attached to the front surface of the pad base f31.

A pair of hook engaging parts f311 are provided at the center of the back side of the pad base f31 in the vertical direction, spaced apart in the left-right direction. The hook engaging parts f311 have engaging holes f314 that are open in the vertical direction.

The hook engaging portion f311 has left and right protruding walls f312 protruding rearward and a connecting wall f313 connecting the rear portions of the left and right protruding walls f312, forming an engaging hole f314 that penetrates in the vertical direction. The hook engaging portion f311 can engage with the base body f2 by inserting a hook f61, which is an engaging portion protruding from the pad body mounting portion f6 of the base body f2, into the engaging hole f314.

The lower part of the rear side of the pad base f31 has left and right fitting protrusions f315 and a central fitting protrusion f316, which serve as engagement parts, at three locations on the left, right and center. Each fitting protrusion f315, f316 is roughly arrow-shaped and protrudes rearward. Each fitting protrusion f315, f316 can engage with a protrusion fitting part f62, which serves as an engagement part, provided on the pad body mounting part f6 of the base body f2. The left and right fitting protrusions f315 are set in a different position from the central fitting protrusion f316. More specifically, the left and right fitting protrusions f315 are set in a position rotated 90 degrees from the central fitting protrusion f316 when viewed from the rear.

[Front skin material f4]
The front skin f4 is made of a fabric having an area larger than the front part of the pad body f3. The edge portion f4e of the front skin f4 can be stored between the pad body f3 and the base body f2 so as not to be visible from the outside. The front skin f4 can form an extended backrest surface fm provided on the backrest surface pm of the upholstery member P.

<Base body f2>
The base body f2 comprises a base plate-shaped portion f5 which is approximately in the shape of an upright plate, a pad body mounting portion f6 which is provided on the front side of the base plate-shaped portion f5 and to which the pad body f1 is attached, an upper frame material mounting portion f7 which is provided below the pad body mounting portion f6 and which is attached to the upper frame material 3 using a screw v1 which is a fastening device, and a rear skin material f9 which covers the peripheral portion and rear surface portion of the base plate-shaped portion f5.

The base plate portion f5, pad body mounting portion f6, and upper frame material mounting portion f7 that constitute the base body f2 are integrally formed from synthetic resin.

In this embodiment, the backrest surface extension member F is configured so that only the rear skin material f9 covering the base plate portion f5 of the base body f2 is visible when viewed from the rear. In other words, the backrest surface extension member F is configured so that no members other than the rear skin material f9 are visible when viewed from the rear.

[Base plate portion f5]
The base plate portion f5 has a generally rectangular shape with its elongated sides in the left-right direction in rear view. The edges of the left and right sides of the base plate portion f5 are gently curved so as to convex outward in rear view. The rear surface of the base plate portion f5 is covered with a rear skin material f9.

The front side of the base plate portion f5 is provided with an upper horizontal rib f52 extending in the left-right direction whose tip can abut against the back surface of the pad base f31, and multiple vertical ribs f53 extending in the up-down direction whose tip can abut against the back surface of the pad base f31. The multiple vertical ribs f53 are arranged at intervals in the left-right direction. A lower horizontal rib f54 extending in the left-right direction whose tip can abut against the upper frame material 3 of the backrest E is provided at the lower part of the front side of the base plate portion f5.

In this embodiment, the movement restriction section ks is mainly composed of the components located behind the upper frame member 3, namely the tip of the lower horizontal rib f54 and the tip of the vertical rib f53 located below the lower horizontal rib f54, and can restrict the forward movement of the backrest surface extension member F by engaging with the back surface of the upper frame member 3.

[Pad body mounting part f6]
The pad body mounting portion f6 has a hook f61 protruding at a position corresponding to the hook engagement portion f311 of the pad base f31, and a protruding engagement portion f62 protruding at positions corresponding to the left, right and central engagement protrusions f316 of the pad base f31.

The pad body f1 is attached to the base body f2 by engaging the hook engagement portion f311 with the hook f61 provided on the pad body attachment portion f6, and then engaging the left, right, and center fitting protrusions f315 and f316 with the protrusion fitting portions f62 provided on the pad body attachment portion f6.

[Upper frame mounting part f7]
The upper frame member mounting portion f7 is mainly composed of a portion that protrudes forward from the lower end of the base plate portion f5. The upper frame member mounting portion f7 has an upward surface f71 that extends in the left-right direction and serves as the mounting base surface for the upper frame member 3.

The upper frame member mounting portion f7 has two screw insertion holes h1 that penetrate vertically on the left and right. The backrest surface extension member F is configured to be attached to the upper frame member 3 by screwing a screw v1 inserted into the screw insertion hole h1 into a nut member J arranged in a nut holding recess nt in the upper frame member 3.

The upper frame mounting portion f7 has a protruding wall portion f72 at the upper end of the front portion corresponding to the portion where the screw insertion hole h1 is formed, which can be positioned at the front opening kh3 of the nut holding recess nt provided in the upper frame 3.

A storage groove f8 that is open downward and outward and can store the edge portion f9e of the rear skin f9 is formed in the lower part of the base body f2, i.e., between the upper frame member mounting portion f7 and the base plate-shaped portion f5. A groove forming wall f73 is erected at the rear end of both sides of the upper frame member mounting portion f7 to form the storage groove f8 between the peripheral portion of the base plate-shaped portion f5.

The front surface of the groove forming wall f73 can abut against the rear surface of the upper frame material 3, and also serves as a movement restriction portion ks that can restrict the forward movement of the backrest surface extension member F.

[Rear skin f9]
The rear skin f9 is made of a material having a larger area than the rear surface of the base plate portion f5. The edge portion f9e of the rear skin f9 can be accommodated between the base plate portion f5 and the pad body f1, and can also be accommodated in an accommodating groove f8 provided between the lower peripheral portion of the base plate portion f5 and the upper frame member mounting portion f7.

<< Hanger G >>
The hanger G is for hanging and fastening a user's clothes, etc. The hanger G is attached to the upper frame member 3 of the back frame M.

The hanger G is equipped with a hanger body g1 extending in the left-right direction for hanging clothes, etc., a pair of left and right hanger legs g2 extending downward from the underside of the hanger body g1 and extending forward at the lower part, and a base portion g3 that connects the lower ends of the left and right hanger legs g2 and has an upper frame member attachment portion g7 that is attached to the upper frame member 3.

The base portion g has a base portion main body g4 on which an upper frame material mounting portion g7 is provided, and a standing wall g5 serving as a movement restriction portion ks that is erected at the rear of the base portion main body g4 and can engage with the rear surface of the upper frame material 3.

The upper frame member mounting portion g7 extends in the left-right direction and has an upward surface g71 that serves as the mounting base surface for the upper frame member 3.

The upper frame member mounting portion g7 has two screw insertion holes h2 that penetrate vertically at the left and right. The hanger G is configured to be attached to the upper frame member 3 by screwing the screw v2 inserted into the screw insertion hole h2 into the nut member J arranged in the nut holding recess nt in the upper frame member 3.

The upper frame mounting portion g7 has a protruding wall portion g72 at the upper end of the front portion corresponding to the portion where the screw insertion hole h2 is formed, which can be positioned at the front opening kh3 of the nut holding recess nt provided in the upper frame 3.

<<How to install the option (backrest extension part F)>>
In the chair of this embodiment, a mounting structure that makes it easy to mount options to the backrest E is applied. Hereinafter, a method of mounting the options to the upper frame material 3 of the backrest E will be described using the backrest surface extension member F as a specific example.

First, the nut member J is held in the nut holding recess nt that is open to the front and provided in the upper frame member 3. A tension member P is pre-attached to the front side of the upper frame portion w1 of the back frame M.

The worker passes the roughly T-shaped nut member J through the upper cavity sa surrounded by the upper frame portion w1 from the rear to the front, and then holds the nut member J in the nut holding recess nt that is open to the front.

The boss portion j1 of the nut member J is accommodated in the nut holding recess nt through the front open portion kh3. The flange portion j2 of the nut member J is accommodated in the gap sk between the nut holding recess nt and the outer frame portion 31. The flange portion j2 of the nut member J engages with the flange portion engagement portion nt3, which is the portion that forms the upper open portion kh1 in the nut holding recess nt, and cannot move downward. In other words, the nut member J is provisionally positioned relative to the upper frame material 3 by having the boss portion j1 accommodated in the nut holding recess nt and the flange portion j2 disposed in the gap sk.

Next, the backrest surface extension member F is moved from rear to front so that the upper frame material placement recess fu is positioned so that it surrounds the upper frame material 3.

Then, a screw v1 is inserted from the bottom to the top through the screw insertion hole h1 provided in the upper frame material mounting portion f7 of the backrest surface extension member F, and the screw v1 is screwed into the boss portion j1 of the nut member J. By screwing the screw v1 into the nut member J, the upper frame material mounting portion f7 of the backrest surface extension member F and the inner frame portion 32 of the upper frame material 3 are tightened.

The above attachment method allows the backrest surface extension member F to be attached to the upper frame material 3 of the backrest E.

The nut holding recess nt provided in the upper frame material 3 is open in the forward and vertical directions, making it easy for the worker to attach (temporarily place) the nut member J. The worker can properly hold the nut member J in the nut holding recess nt by simply feeling the inner frame portion 32 of the upper frame material 3 from the back side of the backrest E, without having to closely check the nut holding recess nt, which is covered by the upholstery member P and difficult to see.

The backrest surface extension member F is also provided with a movement restriction portion ks that can restrict forward movement. Therefore, even if the backrest surface extension member F is pressed forward, the nut member J cannot move forward from the nut holding recess nt that is open to the front side.

<<Locking mechanism V>>
The locking mechanism V is for moving the seat C at a constant ratio in response to the tilting of the backrest E.

The rocking mechanism V in this embodiment has a so-called weight-sensing structure that can appropriately tilt the backrest E in accordance with the weight of the seated person. In other words, the rocking mechanism V is configured to move the seat C backward in conjunction with the backward tilting of the backrest E, while lifting the seat C against the weight of the seated person.

In other words, the rocking mechanism V includes a mechanism for lifting the seat C upward against the weight of the seated person, and is configured to require a backward tilt load proportional to the weight of the seated person in order to tilt the backrest E backward.

The locking mechanism V supports the front part of the seat support c1 so that it can move back and forth via the front shaft jk2 at the front end of the support base B, and pivots the middle part of the seat C in the fore-aft direction on the rear shaft jk3 connected to the front arm part d12.

The rear axle jk3 is disposed in front of and above the main axle jk1 on the left and right arms d1. In this embodiment, the rear axle jk3 is also connected to a bearing axle d4 disposed in the storage space sp of the support base main body 1 via a bearing axle support member d3.

The above-described embodiment can provide a chair having an operating unit main body k11 with a generally cylindrical outer shape that is less complicated, and a reaction force adjustment lever K that can optimally perform the indicator function of indicating the rotational position by the protruding portion k12.

In addition, with the above-described embodiment, the nut member J can be held in the nut holding recess nt that is open upward, downward, and forward, so that a chair having a suitable configuration can be provided in which options such as a backrest surface extension member F can be attached to the backrest E.

In the above-described embodiment, a backrest surface extension member F is attached to the upper frame member 3 of the backrest E. The backrest surface extension member F is configured so that only the rear skin material f9 covering the base plate portion f5 can be seen when viewed from behind, so that a favorable appearance based on the rear skin material f9 can be achieved when viewed from behind.

The above-described embodiment also provides a chair with a suitable configuration in which the lumbar support R, which can support the lower back of a seated person, can be vertically repositioned relative to the backrest E and can be detached without having to attach or detach a fastening device.

In addition, in the above-described embodiment, the tension member P is wound and supported on the intermediate connecting frame member 5, which is a cross member, and therefore not only can the back surface of the intermediate connecting frame member 5 be effectively prevented from being exposed to the outside, but also it is possible to provide a chair with excellent flexibility, allowing the tension member P to be tensioned to the back frame M with an appropriate tension.

In addition, in the above-described embodiment, the tip t21 of the screw head abutment protrusion t2 can engage with the head v61 of the screw v6, so that not only can the screw v6 for attaching the backrest E be concealed to obtain a suitable appearance, but it is also possible to provide a chair having a configuration in which it is possible to check whether the screw v6 is properly attached to the backrest E based on the position of the back frame cap T, which serves as a concealing member.

In addition, the above-mentioned embodiment includes a support base body 1 in which at least the foundation bottom structure 11 and the left and right side walls 14 are integrally molded from synthetic resin, and the left and right side walls 14 of the support base body 1 are formed with recesses 1a recessed in the thickness direction of the side walls 14. This makes it possible to suitably suppress abnormal deformation during molding of the left and right side walls 14, and provides a chair with a suitable configuration that allows the main axis jk1, which is an axis, to be supported by the left and right side walls 14 of the support base body 1 made of synthetic resin.

In addition, recesses 1a are formed in the left and right side walls 14, and these recesses 1a can be used to suitably position the support base body 1 during assembly and disassembly. Therefore, in this embodiment, in order to improve the design and strength of the support base body 1, a suitable external shape having curved surfaces or the like can be designed without difficulty, without having to worry about the difficulty of positioning during the assembly and disassembly processes.

As described above, the chair according to this embodiment is provided with a lumbar support R that can support the lower back of a seated person, and is vertically adjustable relative to the backrest E and can be attached and detached without the need to attach or detach a fastener.

The backrest E is equipped with left and right side frame members 2 that extend in the vertical direction, and a tension member P that is tensioned between the left and right side frame members 2. The left and right side frame members 2 are provided with lumbar support holding portions N that can hold the held portions r22 provided at both the left and right ends of the lumbar support R. The held portions r22 are equipped with upper protruding portions r221 and lower protruding portions r222 that are multiple protruding portions that protrude rearward.

The lumbar support holding portion N is provided with a receiving groove 221 that receives the upper protruding portion r221 and the lower protruding portion r222 and extends in the vertical direction and is open to the front, and a front restricting portion q1 that is disposed in front of the receiving groove 221 and can restrict the forward movement of the upper protruding portion r221 and the lower protruding portion r222.

The side groove forming wall 221b that can form the accommodation groove 221 has an upper notch 221c and a lower notch 221d that allow the upper protruding portion r221 and the lower protruding portion r222 to pass through when attaching or detaching the lumbar support R to the backrest E.

Therefore, this embodiment can provide a chair with a suitable configuration in which the lumbar support R, which can support the lower back of a seated person, can be moved up and down relative to the backrest E, and can be attached and detached without having to attach or detach fasteners such as screws.

In other words, the lumbar support holding portion N is provided with an upper notch 221c and a lower notch 221d through which the upper protruding portion r221 and the lower protruding portion r222 provided on both side ends of the lumbar support R pass. Therefore, after the chair is completed, the lumbar support R can be attached and detached freely to the backrest E, and since the lumbar support R cannot come off the backrest E unless it passes through the limited area of the upper notch 221c and the lower notch 221d, problems such as the lumbar support R unintentionally coming off the backrest E are unlikely to occur.

In addition, by temporarily bending the entire lumbar support R in the thickness direction, the upper protruding portion r221 and the lower protruding portion r222 provided on both sides of the lumbar support R can pass through the upper notch 221c and the lower notch 221d of the lumbar support holding portion N, so that the lumbar support R is less likely to come off unintentionally from the backrest E.

The held portion r22 has an upper protruding portion r221 and a lower protruding portion r222 that are multiple protruding portions spaced apart in the vertical direction. The groove forming wall 221b on the side is provided with an upper notch 221c that is a notch that allows the upper protruding portion r221 to pass through, and a lower notch 221d that is a notch that allows the lower protruding portion r222 to pass through.

As a result, not only is the posture of the lumbar support R easily maintained, but the lumbar support R is also provided with an appropriate configuration that makes it difficult for the lumbar support R to suddenly come off the lumbar support holding portion N.

The shape of the upper protruding portion r221 is set to a different shape than the shape of the lower protruding portion r222.

The shape of the upper cutout 221c is set to correspond to the upper protruding portion r221 so that the upper protruding portion r221 can pass through, and the shape of the lower cutout 221d is set to correspond to the lower protruding portion r222 so that the lower protruding portion r222 can pass through.

Therefore, in this embodiment, the lumbar support R is preferably prevented from being attached incorrectly to the backrest E in an upside-down manner.

The front restricting portion q1 is a separate member from the side frame material 2 and is provided on the retaining member Q that is attached to the side frame material 2.

For this reason, the front restricting portion q1 has a suitable configuration that allows it to be disposed in front of the accommodation groove 221.

The lumbar support holding portion N can hold the upper protruding portion r221 and the lower protruding portion r222 in the front-rear direction by the front restricting portion q1 and the rear groove forming wall 221a that can form the accommodation groove 221.

For this reason, the lumbar support holding portion N is configured to sandwich the upper protruding portion r221 and the lower protruding portion r222 from the front-rear direction, so that the lumbar support R can be appropriately held at a predetermined height position so that the lumbar support R does not fall downward due to its own weight.

The lumbar support R comprises a lumbar support main body r1 and left and right arm members r2 supported by the lumbar support main body r1. The left and right arm members r2 have retained portions r22 at their outer ends.

For this reason, the lumbar support R has a suitable configuration for providing the retained portion r22 at both outer ends.

The left and right arm members r2 are supported so that they can move left and right relative to the lumbar support body r1.

This allows the lumbar support R to be attached and detached with great flexibility to the lumbar support holding portion N provided on the backrest E. In other words, by moving the left and right arm members r2, which can move in the left-right direction, toward the center of the lumbar support main body r1, the lumbar support R can be properly attached to the lumbar support holding portion N without excessively bending the entire lumbar support R in the thickness direction.

The upper convex portion r126 and the lower convex portion r127, which are the first engagement portion provided on the lumbar support main body r1, engage with the upper engagement hole r213 and the lower engagement hole r214, which are the second engagement portion provided on the left and right arm materials r2, so that the left and right arm materials r2 are configured to be movable in the left and right direction relative to the lumbar support main body r1.

Therefore, in this embodiment, the left and right arm members r2 are preferably configured to be movable in the left-right direction relative to the lumbar support body r1.

The lumbar support body r1 comprises a front body member r11 and a rear body member r12 that is approximately the same size as the front body member r11 and is attached to the rear side of the front body member r11, and the left and right arm members r2 are sandwiched between the front body member r11 and the rear body member r12.

For this reason, in this embodiment, not only can the lumbar support main body r1 have a suitable configuration with excellent appearance, but it is also easy to adopt a configuration in which the left and right arm members r2 can be supported so as to be movable in the left-right direction relative to the lumbar support main body r1.

The front body member r11 comprises a front body base r111 made of synthetic resin in the shape of a plate extending in the left-right direction, and a front skin material r112 that covers the front surface and peripheral edge of the front body base r111, and the rear body member r12 comprises a rear body base r121 made of synthetic resin in the shape of a plate extending in the left-right direction, and a rear skin material r122 that covers the rear surface and peripheral edge of the rear body base r121.

As a result, the front body base r111 covered by the front skin material r112 and the rear body base r121 covered by the rear skin material r122 allow the lumbar support body r1 to exhibit a favorable appearance based on the front skin material r112 and the rear skin material r122.

The present invention is not limited to the embodiments described above.

The cutout that allows the protruding portion to pass through may be provided in the front restricting portion. In other words, the chair is provided with a lumbar support that can support the waist of a seated person, and is vertically repositionable with respect to the backrest and can be attached and detached without attaching or detaching a fastener, the backrest is provided with left and right side frame members that extend in the vertical direction and a tension member that is stretched between the left and right side frame members, the left and right side frame members are provided with lumbar support holding portions that can hold the held portions provided at both left and right ends of the lumbar support, the held portions have one or more protruding portions that protrude backward, the lumbar support holding portion has a receiving groove that receives the protruding portion, extends in the vertical direction, and is open to the front, and a front restricting portion that is provided in front of the receiving groove and can restrict the forward movement of the protruding portion, and the front restricting portion may be provided with a cutout that allows the protruding portion to pass through when the lumbar support is attached and detached from the backrest.

The held portion may have upper and lower protruding portions that are multiple protruding portions spaced apart in the vertical direction, and the front restricting portion may be provided with upper cutouts that allow the upper protruding portions to pass through, and lower cutouts that allow the lower protruding portions to pass through.

For a more specific explanation, other embodiments of the lumbar support R and the lumbar support holding portion N will be described below with reference to Figures 63 to 70.

In another embodiment, the lumbar support holder N has an upper notch q11 and a lower notch q12 that are provided in a holder Q that is configured separately from the back frame M.

That is, the lumbar support holding portion N is provided with an accommodation groove 221 that extends in the vertical direction and is open forward and that accommodates the upper protruding portion r221 and the lower protruding portion r222, which are multiple, i.e., two, protruding portions provided on the held portion r22 of the lumbar support R, and a holding member Q that is disposed in front of the accommodation groove 22 and has a front restricting portion q1 that can restrict the forward movement of the upper protruding portion r221 and the lower protruding portion r222.

Between the front restricting portion q1 of the retaining member Q and the side groove forming wall 221 of the accommodation groove 221, a communication space sc extending in the vertical direction is formed through which the retained portions r22 of the left and right arm materials r2 of the lumbar support R, which have an upper protruding portion r221, a lower protruding portion r222, and a protruding portion 220 at their tips, can communicate.

In this embodiment, two notches, an upper notch q11 and a lower notch q12, are formed in the holding member Q.

The accommodation groove 221 is mainly formed by a rear groove forming wall 221a and a side groove forming wall 221b that engage with the retained portion r22. The accommodation groove 221 is provided with a rear groove forming wall 221a located on the rear side of the upper protruding portion r221 and the lower protruding portion r222, and a side groove forming wall 221b that extends forward from the inner side of the rear groove forming wall 221a and is located on the inner side of the upper protruding portion r221 and the lower protruding portion r222.

In this embodiment, unlike the above-mentioned embodiment, no cutout is formed in the side groove forming wall 221b.

The retaining member Q extends in the vertical direction and includes a front restricting portion q1 that is disposed in front of the accommodation groove 221 and can restrict the forward movement of the upper protruding portion r221 and the lower protruding portion r222 of the lumbar support R by abutting against the upper protruding portion r221 and the lower protruding portion r222, an attachment portion q2 that is connected to the upper and lower ends of the front restricting portion q1 and has a screw insertion hole h3 that penetrates in the front-rear direction, and a positioning wall q3 that extends from the outer side of the front restricting portion q1 toward the rear, i.e., toward the inner frame portion 22, and is disposed between the accommodation groove 221 and the outer frame portion 21.

The front restricting portion q1 is shaped like a rail extending in the vertical direction. The front restricting portion q1 is capable of clamping the upper protruding portion r221 and the lower protruding portion r222 in the front-rear direction by cooperating with the inner groove forming wall 221a that can form the accommodation groove 221.

The front restricting portion q1 has an upper notch q11 and a lower notch q12 that allow the upper protruding portion r221 and the lower protruding portion r222 to pass through when attaching or detaching the lumbar support R to the backrest E.

That is, the front restricting portion q1 has an upper notch q11 through which the upper protruding portion r221 can pass when the lumbar support R is attached to or detached from the backrest E, and a lower notch q12 through which the lower protruding portion r222 can pass. The upper notch q11 and the lower notch q12 are open inward and upward.

The upper cutout q11 and the lower cutout q12 are formed spaced apart above and below the front restricting portion q1. The upper cutout q11 and the lower cutout q12 are each provided in the upper half of the front restricting portion q1.

The supported portion r22 of the lumbar support R is provided with a eaves-like protruding portion r220 that connects the upper protruding portion r221 and the lower protruding portion r222 and protrudes outward from the outer end of the arm base r21 (i.e., the outer end of the horizontal extension portion r218 in the outer plate portion r212).

As a result, when the lumbar support R, which can move up and down relative to the backrest E, is positioned at the top of the lumbar support holding portion N, even if the upper protruding portion r221 and the lower protruding portion r222 of the lumbar support R are in a position facing the upper notch portion q11 and the lower notch portion q12 in the front restricting portion q1, the lumbar support R is unlikely to come off the lumbar support holding portion N.

In other words, even if the held portion r22 of the lumbar support R moves forward, the eave-shaped protrusion r220 provided on the held portion r22 can engage with the front restriction portion q1 located in front of it. Therefore, the forward movement of the held portion r22 of the lumbar support R is appropriately restricted, and the lumbar support R is unlikely to come off the lumbar support holding portion N.

As in the above-described embodiment, the shapes of the upper protruding portion r221 and the lower protruding portion r222 may be different, and the shape of the upper notch q11 corresponding to the upper protruding portion r221 and the shape of the lower notch q12 corresponding to the lower protruding portion r222 may of course be different.

Needless to say, the present invention is not limited to the above-mentioned embodiments.

The tensioning member need only be stretched between the left and right side frame members, and is not limited to the embodiment described above.

The held portion may have only a single protruding portion protruding rearward, or may have three or more protruding portions.

The front restriction portion may have any configuration as long as it is disposed in front of the storage groove and is capable of restricting the forward movement of the protruding portion.

The notch is provided in the front restriction portion or the groove-forming wall on the side, and it is sufficient that the protruding portion can pass through when the lumbar support is attached to or detached from the backrest, and it goes without saying that the specific shape can be set in a variety of ways.

The shape of the upper protruding portion that constitutes the retained portion may not differ from the shape of the lower protruding portion.

The front restricting portion may not be a separate member from the side frame material. In other words, the front restricting portion may be an integrally formed part that can constitute the side frame material.

The lumbar support may be made entirely of synthetic resin.

For example, the lumbar support body and the left and right arm members that make up the lumbar support may be integrally formed from synthetic resin.

The lumbar support is not limited to the one shown in the above-mentioned embodiment in which the left and right arm members are supported so as to be movable in the left and right direction relative to the lumbar support main body, but may be one in which the left and right arm members are not supported so as to be movable in the left and right direction relative to the lumbar support main body.

The first engagement portion provided on the lumbar support body may be configured as an engagement hole that is longer in the width direction than the convex portion, and the second engagement portions provided on the left and right arm members may be configured as convex portions that can engage with the engagement holes.

For example, the inner plate-like portion of the arm base of the left and right arm members may be provided with a front protruding convex portion that protrudes forward and a rear protruding convex portion that protrudes rearward, and these may be engaged with engagement holes corresponding to the front protruding convex portion provided in the front main body member of the lumbar support body, and also engaged with engagement holes corresponding to the rear protruding convex portion provided in the rear main body member.

The left and right arm members may not be sandwiched between the front and rear body members.

The front and rear body members may not be covered with a skin material.

The specific configuration of each part is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the present invention.

E: backrest 2: side frame material P: upholstery member R: lumbar support N: lumbar support holder 221: accommodation groove 221c: upper cutout (cutout)
221d...lower notch (notch)
r22...Holded part r221...Upper protruding part (protruding part)
r222...Lower protruding part (protruding part)
q1...Front restriction part

Claims (10)

A chair in which a lumbar support capable of supporting the lower back of a seated person is provided so that the position of the lumbar support can be changed in the vertical direction relative to the backrest and the lumbar support can be attached and detached without attaching and detaching a fastening device,
The backrest is provided with left and right side frame members extending in the vertical direction and a tension member stretched between the left and right side frame members,
The left and right side frame members are provided with lumbar support holding portions capable of holding held portions provided at both left and right ends of the lumbar support,
The held portion has one or more protruding portions protruding rearward,
the lumbar support holding portion includes an accommodation groove that accommodates the protruding portion, extends in the vertical direction, and is open to the front, and a front restricting portion that is disposed in front of the accommodation groove and can restrict forward movement of the protruding portion,
A chair in which a cutout portion is provided in the groove forming wall of the front regulating portion or the side portion that can form the storage groove, through which the protruding portion can pass when the lumbar support is attached or detached from the backrest. The held portion includes upper and lower protruding portions that are the plurality of protruding portions arranged at intervals in the vertical direction,
The chair according to claim 1, wherein the front regulating portion or the groove forming wall is provided with an upper notch which is the notch through which the upper protruding portion can pass, and a lower notch which is the notch through which the lower protruding portion can pass. The shape of the upper protruding portion is set to be different from the shape of the lower protruding portion,
the shape of the upper cutout portion is set to correspond to the upper protruding portion so as to allow the upper protruding portion to pass therethrough;
3. The chair according to claim 2, wherein the shape of said lower cutout portion is set to a shape corresponding to that of said lower protruding portion so as to allow said lower protruding portion to pass therethrough. A chair according to claim 1, 2 or 3, in which the front restraining portion is a separate member from the side frame material and is provided on a retaining member attached to the side frame material. The chair according to claim 1, 2, 3 or 4, in which the lumbar support holding portion can hold the protruding portion by sandwiching it in the front-rear direction between the front restricting portion and the inner groove forming wall capable of forming the storage groove. The lumbar support includes a lumbar support body and left and right arm members supported by the lumbar support body,
6. A chair according to claim 1, 2, 3, 4 or 5, wherein the supported portions are provided on outer ends of the left and right arm members. The chair according to claim 6, wherein the left and right arm members are supported so as to be movable in the left and right direction relative to the lumbar support body. A first engagement portion provided on the lumbar support body engages with a second engagement portion provided on the left and right arm members, so that the left and right arm members are movable in the left and right direction relative to the lumbar support body,
the first engagement portion is configured by a convex portion or an engagement hole that is longer in a width direction than the convex portion,
8. The chair according to claim 7, wherein the second engagement portion is configured by an engagement hole capable of engaging with the convex portion or a convex portion capable of engaging with the engagement hole. The lumbar support body includes a front body member and a rear body member that is substantially the same size as the front body member and is attached to the rear side of the front body member,
9. A chair according to claim 6, 7 or 8, wherein the left and right arm members are sandwiched between the front body member and the rear body member. the front body member includes a front body base made of synthetic resin and formed in a plate shape extending in the left-right direction, and a front skin material covering a front surface and a peripheral edge portion of the front body base,
10. The chair according to claim 9, wherein the rear body member comprises a rear body base made of synthetic resin in the form of a plate extending in the left-right direction, and a rear covering material covering the rear surface and peripheral portion of the rear body base.

Images